The invention relates generally to semiconductor device and integrated circuit fabrication and, in particular, to device structures and fabrication methods for an on-chip resistor.
On-chip resistors are passive devices found in many integrated circuits. An on-chip resistor may be formed by depositing a layer of resistor material having a given thickness and patterning the resistor material layer to provide a resistor body that is dimensioned to a particular length and width. The resistance of an on-chip resistor is based on a combination of physical properties (i.e., cross-sectional area and length) and material properties (e.g., resistivity). An on-chip resistor may be coupled with an external load resistor of fixed resistance.
During operation, the temperature of an on-chip resistor changes due to Joule heating. The resistivity of the resistor material may vary widely as a function of temperature. The variation of the resistivity is governed by the temperature coefficient of resistance (TCR) of the resistor material. The TCR of the resistor material may be adjusted or tuned at the time of design and fabrication through an adjustment in material properties, such as resistor thickness, the doping level in the resistor material, the grain size of polycrystalline resistor material, and/or the composition of the resistor material.
Improved device structures and fabrication methods for an on-chip resistor are needed.